This invention relates to optical pyrometers and the technique for making temperature measurements and particularly to utilizing two detectors having their wavelength interval such that one is contained within the other.
This invention is particularly efficacious for use in temperature measurement of a turbine in a jet engine where the combustion flame produces reflected energy that adversely affects the measured temperature of the turbine. Optical pyrometers are well known measurement apparatus utilized in measuring temperature typically above the effective range of thermocouples or where a noncontact measurement is required. The heretofore known optical pyrometer typically employs one or two different wavelength intervals, however, in this system instead of a single color or the two color pyrometer, a split color technique is employed such that one wavelength interval is contained in the other.
Where in an environment as the jet engine, the combustion flame is hotter than the turbine surface, because the two pyrometers selected have different wavelength bands, each will be affected differently by the reflected energy. Hence, the spectral range of the two pyrometers are selected so that a reflected component is evidenced from the temperature differences. When both linearized pyrometer outputs are equal, no reflective error will be present. However, upon disagreement of the pyrometer, in accordance with this invention, these outputs can be utilized to calculate an approximation of the magnitude of the reflection error.